Background patents include U.S. Pat. No. 7,409,899 (899 patent) entitled “Optical detection and location of gunfire,” by Beekman, hereby incorporated by reference. The '899 patent discloses an optical gunfire detection system comprising an image-capturing device operable for detecting light; a narrowband Fraunhofer line filter connected to the image-capturing device, and operable for partially restricting transmission of the light; a convex parabolic reflector operable for transmitting images to the image-capturing device; a lens system; an image storage device connected to the image-capturing device, wherein the image storage device comprises a solid-state digital memory unit operable to store multiple seconds of video imagery; a real-time computer-implemented mechanism connected to the image storage device, the computer-implemented mechanism operable for detecting locations and classifications of gunfire associated with the images; an acoustic device in communication with the computer-implemented mechanism, and operable for verifying the classifications of the gunfire; a position laser operable for identifying the locations of the gunfire; and a defense mechanism comprising the laser pointer and operable to defend against a source of the gunfire.
U.S. Pat. No. 5,686,889, hereby incorporated by reference, entitled “Infrared sniper detection enhancement,” to Hillis is directed to the concept that firing of small arms results in a muzzle flash that produces a distinctive signature conducive to automated or machine-aided detection with an IR (infrared) imager. The muzzle flash is intense and abrupt in the 3 to 5μ band. A sniper detection system operating in the 3 to 5μ region must deal with the potential problem of false alarms from solar clutter. The invention reduces the false alarm rate of an IR based muzzle flash or bullet tracking system (during day time) by adding a visible light (standard video) camera. A standard video camera helps detect (and then discount) potential sources of false alarm caused by solar clutter. If a flash is detected in both the IR and the visible spectrum at the same time, then the flash is most probably the result of solar clutter from a moving object. If a flash is detected only in the IR, then it is most probably a true weapon firing event.
U.S. Pat. No. 5,612,676, entitled “Dual channel multi-spectrum infrared optical fire and explosion detection system,” to Plimpton, discloses a fire detection system including two optical sensing channels and signal processing circuitry that processes the two sensing channels' output signals and generates another output signal when the processed signals are indicative of a fire. The system automatically detects hydrocarbon and certain nonhydrocarbon fueled fires.
U.S. Pat. No. 7,432,498 entitled “Method and apparatus for optically detecting and identifying a threat,” to Capron, discloses an optical detection apparatus includes a housing having a circumferential opening therein. A primary mirror reflects light rays to form a first set of light rays to a secondary mirror that has a generally concave shape coupled to the housing.
Currently, there is a great need to quickly identify the direction and location of small arms fire experience by the war fighter, i.e., the location of a sniper. This problem is compounded when the soldier is operating in cavernous/mountainous or urban regions where acoustic cues are ineffective. A primary hazard facing soldiers on the battlefield is the ever increasing threat of being injured by sniper attack, This threat exists in both rural and urban environments. There are numerous efforts to develop instrumentation capable of detecting the direction and/or location of a rougue sniper. Usually these techniques are based on either an acoustic signal from the small arms fire, or the detection of the resultant thermal signature as recorded by an IR sensor. However, both systems require instrumentation that is fairly large and expensive and not appropriate for being deployed on each and every soldiers who needs such protection. In addition, systems based on acoustic triangulation are prone to inaccuracies due to multiple acoustic reflections, and optical detection methods that use thermal signature are very costly and suffer from frequent false alarm rates.
Accordingly there is need for a method and/or device which addresses all concerns related to: 1) the detectability of a weak optical signal that results when a small arm is fired, 2) the accuracy and reliability of a triggered event, i,e. low false alarm rates, 3) portability so that the envisioned device adds no appreciable weight or size to the current soldier's payload, and 4) economical cost for each unit at a price point low enough as to allow for large scale deployment.